Force all traffic to go through the router

I am a small ISP in easter washington. The PUD operates the fiber network that I then resell to my customers. The PUD doesnt let the customers talk to each other on the network, I think its called client isolation. Meaning that for video gamers they are not cannot play games with each other. They can only play an xbox live game if someone outside our network hosts it.

I talked to the PUD and they said the are not going to change the way it is set up, because they want to charge extra to businesses to connect two locations together. The PUD guy said to maybe try forcing all the traffic to go through the router. He said he wasnt sure what it was called, but he called it host only addressing.

I was wondering if anyone knew how to do this, had a different way for clients to talk to other clients.
Thanks

Hi, a network map please , how your clients connected to you , you have Mikrotik router ? more details

but i think you can run a private L2TP server on your router , whenever your customer wanna play game , they can connect to your router via L2TP and even Layer 2 traffic will be passed ! like bridging